SOLVED! Intermittent metallic noise consistent with wheel speed

6716

Well-Known Member
Hey All! I'm back. Never did sell the Trailblazer. Couldn't let go of it. I'm back on the road with it.

The issue: there is an intermittent metallic-ish squeaking consistent with wheel speed that tends to occur at lower speeds, though I think I have heard it whining intermittently at 35-miles-ish an hour. It is most noticeable at take-off and coming to a stop. It sounds about the same at take-off and stopping, and it doesn't change whether the brake pedal is depressed or not. If I go from stop and hit the throttle hard, it seems to go away under acceleration but return again when I am off the throttle, and this is true even if I am just spinning the back wheels in the snow. It sounds like it is coming from up front, sort of center-ish, maybe.

The truck has been mostly sitting for the last almost four years, due to transmission issues which are (mostly?) fixed (still a little leak, still have to figure that out). I pulled the transmission down, had it rebuilt, and put it back up.

I almost wonder if it is the front propeller shaft, though that doesn't make a ton of sense. Could be a brake issue. Dude at the oil change today guessed hub, but his guess is as good as anyone else's.

Any thoughts on how to narrow down the toubleshooting?
 

MRRSM

Lifetime VIP Supporter
That symptom is consistent with the Built-In Safety Warning Break Wear Indicator on your Brake Pads activating. It will be worthwhile pulling BOTH front Wheels, Calipers and Pads and if convenient... Have ALL of the required Replacement Parts on hand and the time to perform the proper R&R if you find they are worn well beyond your expectations.

These must be replaced in Pairs; either at the Front or the Rear as complete sets if you discover the "Spring Steel Wear Tab" is level and even with the remaining Disc Pad material. ChrisFix has Excellent "How To' Videos for this particular R&R:

How to FIX Them:


How to BLEED them:

 
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Mooseman

Moderator
Could be a couple of things. As mentioned by @MRRSM , could be the brake wear indicator. Could also be a dust shield rubbing on a rotor or something in the parking brake.
 
OP
6716

6716

Well-Known Member
That symptom is consistent with the Built-In Safety Warning Break Wear Indicator on your Brake Pads. It will be worthwhile pulling BOTH front Wheels, Calipers and Pads and if convenient... Have ALL of the required Replacement Parts on hand and the time to perform the proper R&R if you find they are worn well beyond your expectations.

Yeah probably not a bad idea to pull the wheels and look at the pads. I feel like they should have lots of life in them, but that is just a vague feeling based on when I think I replaced them last.

Could be a couple of things. As mentioned by @MRRSM , could be the brake wear indicator. Could also be a dust shield rubbing on a rotor or something in the parking brake.

I had an issue with the dust shield a while back. I'll check that as well. I'm thinking not parking brake since it is all in the front.

Thanks to you both for your replies.
 

gpking

Well-Known Member
The issue: there is an intermittent metallic-ish squeaking consistent with wheel speed that tends to occur at lower speeds, though I think I have heard it whining intermittently at 35-miles-ish an hour. It is most noticeable at take-off and coming to a stop. It sounds about the same at take-off and stopping, and it doesn't change whether the brake pedal is depressed or not. If I go from stop and hit the throttle hard, it seems to go away under acceleration but return again when I am off the throttle, and this is true even if I am just spinning the back wheels in the snow. It sounds like it is coming from up front, sort of center-ish, maybe.
When I had an at-speed noise I couldn't solve, I started by jacking up the rear end and letting the engine idle in Drive while I walked around listening. It is almost impossible to tell where a mystery sound is coming from inside the vehicle. Just start by isolating whatever parts you (safely) can.

The noise I thought was a rubbing dust shield (which continued after I angrily cut all 4 off) actually turned out to be the abutment clips on the brakes rubbing the rotors once they heated up and expanded ever so slightly now that they are warped a bit with age. It would only happen once the brakes were heated and only was audible below like 45 mph. But it sounded more like a shk,shk,shk,shk metal rubbing crusty metal noise.
I have to grind the rust off the edges of the rotors at least once a year to keep the noise from coming back.
 

MRRSM

Lifetime VIP Supporter
What @gpking describes makes perfect sense. Look at the facts. The Sheer MASS of the Disk would definitely expand outwards after the Iron Molecules combine with Oxygen in the presence of Salty-Slush Water and bulge like some Grandad trying to squeeze his Belly into his original Wedding Tux:

FE203WEIGHSMORETHANIRON.jpg
 
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OP
6716

6716

Well-Known Member
The noise I thought was a rubbing dust shield (which continued after I angrily cut all 4 off) actually turned out to be the abutment clips on the brakes rubbing the rotors once they heated up and expanded ever so slightly now that they are warped a bit with age. It would only happen once the brakes were heated and only was audible below like 45 mph. But it sounded more like a shk,shk,shk,shk metal rubbing crusty metal noise.
I have to grind the rust off the edges of the rotors at least once a year to keep the noise from coming back.

That kind of sounds like what I am hearing. I might put up the front end and spin the wheels and see what I hear (if I can find a garage to work in). Now that you remind me I could take a video of the sound, I might do that as well.

The issue seems to be lessened as I drive the Trailblazer more and more. We just got a bunch of snow, and I have been super pleased to be driving the truck and not my Jetta (which does well enough in some snow, but it just doesn't have the clearance to get over the plow slop at intersections).
 
OP
6716

6716

Well-Known Member
Found the squeak! Turns out, if you only put in ONE of the caliper slide pins the caliper can float up and rub on the rim.

I feel kinda stupid it took me this long to figure it out but I am finally going after the CV axle and noticed it when I went to take the caliper off.

You can see where the caliper bump is ground flat and also the track it made on the rim.
 

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